Conventionally, a pole position is detected using a magnetic pole detector and an AC synchronous motor is controlled based on the pole position thus detected. However, there is a problem in that a cost is increased and a reliability is reduced due to providing the magnetic pole detector. In particular, a magnetic pole detector corresponding to an operating range of a motor is required in a linear motor. For this reason, the problem is remarkable. In order to solve the problem, pole position estimating means is used for estimating an initial magnetic pole of an AC synchronous motor without using the magnetic pole detector.
A conventional initial pole position estimating apparatus for an AC synchronous motor selects a first or second cycle section in accordance with results of a speed gain control portion and mode section deciding means. The initial pole position estimating apparatus includes first torque calculating means when the first cycle section is selected, and second torque calculating means when the second cycle section is selected, and calculates an estimated pole position using torque data obtained by the first and second torque calculating means (e.g., see Patent Document 1 and Patent Document 2).
FIG. 8 is a diagram showing a conventional initial pole position estimating apparatus and method for an AC synchronous motor. In FIG. 8, 1301 denotes command speed pattern generating means, 1302 denotes mode section deciding means, 1303 denotes speed integration gain processing means, 1304 denotes a mode switch, 1101 denotes a first cycle section (a q-axis command current is a command torque and a d-axis command current is zero), 1102 denotes data acquiring speed section deciding means, 1103 denotes first command current calculating means, 1104 denotes first memory storing means, 1201 denotes a second cycle section (a q-axis command current is zero and a d-axis command current is a command torque), 1202 denotes data acquiring speed section deciding means, 1203 denotes second command current calculating means, and 1204 denotes second memory storing means.
An AC synchronous motor control device comprises speed control means for calculating a command torque (a command current) from a command speed, and current control means and a PWM power converting device, each of which serve to drive an AC synchronous motor in response to a command torque (a command current). The AC synchronous motor control device serves to calculate an estimated initial pole position using information of the first command torque data (the first command current data) and the second command torque data (the second command current data) through speed deviation calculating means for subtracting the detected speed from the command speed generated from the command speed pattern generating means 1301 to calculate a speed deviation; a speed gain control portion for multiplying the speed deviation by a speed gain, thereby calculating a command torque (a command current); the mode section deciding means 1302 for carrying out a processing of deciding the mode section (the first cycle section 1101 and the second cycle section 1201) from the command speed; the mode switch 1304 for carrying out switching into either the first cycle section 1101 or the second cycle section 1201 in accordance with a result obtained by the mode section deciding means 1302; the data acquiring speed section deciding means 1102 for deciding whether the command speed is in a data acquiring speed section or not when the first cycle section 1101 is selected; the first command torque calculating means (the first command current calculating means) 1103 for calculating first command torque data (first command current data) from the command torque (the command current) in the data acquiring speed section thus decided; the data acquiring speed section deciding means 1202 for deciding whether the command speed is in the data acquiring speed section or not when the second cycle section 1201 is selected; and the second command torque calculating means (the second command current calculating means) 1203 for calculating second command torque data (second command current data) from the command torque (the command current) in the data acquiring speed section thus decided.
Patent Document 1: JP-A-2001-157482 Publication (see Pages 9 to 13, FIG. 3)
Patent Document 2: JP-A-2003-111477 Publication (see Page 8, FIGS. 17 and 18)